Biomedical subjects

S H Oh

Publications and source records attributed to S H Oh.

At least 109 records · Page 6Linked to original sources

PubMed1993

Isoelectric focusing subtypes of HLA-A can be defined by oligonucleotide typing.

This study describes a simple and direct method for sequence-specific oligonucleotide probe (SSOP) typing of the A locus of HLA class I genes. Genomic DNA from a panel of over 200 cells which have been characterized by the methods of serology and isoelectric focusing (IEF) for the HLA class I antigens was used for locus-specific PCR amplification of HLA-A sequences. Dot blot hybridization of the amplified products was performed with 28 SSOPs derived from hypervariable regions in exon 2 and 3. Co-amplification of three alleles of HLA-H pseudogene in apparent linkage disequilibrium with HLA-A2 and A10 was observed but did not interfere with the typing of HLA-A alleles. Using short SSOPs (15 nucleotides each) in single temperature tetramethylammonium chloride (TMAC) hybridization and washing steps, 30 IEF-definable isotypes of HLA-A antigens could be unambiguously defined by their hybridization patterns. Moreover, comparison of the typing results with available nucleotide sequences of HLA-A alleles showed that the conditions used allowed faithful detection of single codon mismatches between probe and template. Thus, these alleles can be identified by their unique hybridization patterns generated by the SSOPs. Nucleotide sequence analysis of any new HLA-A allele will further permit its rapid and unambiguous characterization by SSOP typing.

Amino Acid Sequence↗

PubMed1993

Distribution of Borrelia burgdorferi specific antibody among patients with juvenile rheumatoid arthritis in Korea.

Lyme disease, a multi-systemic infection occurring worldwide, has yet to be reported in Korea, although the spirochete B. burgdorferi, known as the causative organism of the disease, has recently been isolated from the vector tick Ixodes persulcatus in the region. To contribute to revealing whether Lyme disease exists in Korea or not, B. burgdorferi specific antibodies (IgG, IgM, and/or IgA) were measured by three individual enzyme-linked immunosorbent assays (ELISA) utilizing different antigens in 38 patients with juvenile rheumatoid arthritis (JRA) which shares a number of clinical features with Lyme arthritis. The antibody prevalence rates in patients with JRA were various depending on the antigens (21% of IgG and IgM antibodies to purified organisms, 0% for IgG antibody to purified native flagella, and 5% for IgG, IgM, and IgA antibodies to recombinant p39) and were not different compared to 39 controls (21%, 0%, and 0% respectively). The antibody prevalence rates compared in various subgroups of patients with JRA according to types of JRA, length of illness, age, and sex were not different. Comparing the three different antigens, the greatest number of positive responders were yielded by purified organisms followed by p39 and purified flagellin, however the possibility of nonspecificity with purified organisms remained. The data indicate that serologic tests using ELISA fail to illustrate Lyme disease among 38 patients with JRA in Korea.

Adolescent↗

PubMed1992

Presence and release of immunoreactive atrial natriuretic peptide in granulosa cells of the pig ovarian follicle.

Atrial natriuretic peptide (ANP) has been reported to be locally synthesized in the ovary although its physiological roles are still unknown. To define the origin of ovarian ANP, we demonstrated the presence and release of immunoreactive (ir) ANP in pig granulosa cells and characterized its biochemical properties. Serial dilution curves made with the extracts of pig granulosa cells, their perfusates and follicular fluid were paralleled to the standard curve of ANP. The amount of irANP in the granulosa cell was 2 fg/cell. The total amount of irANP in granulosa cells significantly correlated with the levels of irANP in follicular fluid. Additionally, the total content of irANP in the follicle negatively correlated with the follicular size. On reverse phase HPLC, the major form of irANP in granulosa cells and follicular fluid was high molecular weight but that in perfusate was low molecular weight. In Northern blot analysis, ANP mRNA was detected in the pig granulosa cells. Immunohistochemistry showed ANP prohormone location in granulosa cells of rat ovary. These data strongly suggest that the granulosa cells synthesize and secrete ANP.

Animals↗

PubMed1992

Expression of a calmodulin methylation mutant affects the growth and development of transgenic tobacco plants.

Transgenic plants were constructed that express two foreign calmodulins (VU-1 and VU-3 calmodulins) derived from a cloned synthetic calmodulin gene. VU-1 calmodulin, similar to endogenous plant calmodulin, possesses a lysine residue at position 115 and undergoes posttranslational methylation. VU-3 calmodulin is a site-directed mutant of VU-1 calmodulin that is identical in sequence except for the substitution of an arginine at position 115 and thus is incapable of methylation. Both calmodulin genes, under the control of the cauliflower mosaic virus 35S promoter, were expressed in transgenic tobacco. Foreign calmodulin protein accumulated in plant tissues to levels equivalent to that of the endogenous calmodulin. All transformed lines of VU-1 plants were indistinguishable from untransformed controls with respect to growth and development. However, all transformed lines of VU-3 plants were characterized by decreased stem internode growth, reduced seed production, and reduced seed and pollen viability. The data suggest that these phenotypes are the result of the expression of the calmodulin mutant rather than the position of transferred DNA insertion or the overall alteration of calmodulin levels. Analyses of the activity of the purified transgenic calmodulins suggest that calmodulin-dependent NAD kinase is among the potential targets that may have altered regulation in VU-3 transgenic plants.

Amino Acid Sequence↗

PubMed1992

Modulation of calmodulin levels, calmodulin methylation, and calmodulin binding proteins during carrot cell growth and embryogenesis.

Carrot cell cultures were used to study the dynamics of calmodulin protein levels, calmodulin methylation, and calmodulin-binding proteins during plant growth and development. Comparisons of proliferating and nonproliferating wild carrot cells show that, while calmodulin protein levels does not vary significantly, substantial variation in post-translational methylation of calmodulin on lysine-115 is observed. Calmodulin methylation is low during the lag and early exponential stages, but increases substantially as exponential growth proceeds and becomes maximal in the postexponential phase. Unmethylated calmodulin quickly reappears within 12 h of reinoculation of cells into fresh media, suggesting that the process is regulated according to the cell growth state. Calmodulin and calmodulin-binding proteins were also analyzed during the formation and germination of domestic carrot embryos in culture. Neither calmodulin methylation nor calmodulin protein levels varied significantly during somatic embryogenesis. However, upon germination of embryos, the level of calmodulin protein doubled. By calmodulin overlay analysis, we have detected a major 54,000 M(r) calmodulin-binding protein that also increased during embryo germination. This protein was purified from carrot embryo extracts by calmodulin-Sepharose chromatography. Overall, the data suggest that calmodulin methylation is regulated depending upon the state of cell growth and that calmodulin and its target proteins are modulated during early plant development.

Calmodulin↗

PubMed1992

Frog lymph heart synthesizes and stores immunoreactive atrial natriuretic peptide.

The presence of immunoreactive atrial natriuretic peptide (irANP) and ANP gene expression in the frog lymph heart was examined by a radioimmunoassay (RIA) combined with HPLC and by Northern blot hybridization of total RNA. Serial dilution curve of the lymph heart extract was paralleled with the RIA standard curve. The lymph heart contained 153.32 +/- 35.80 pg of irANP/mg of wet tissue. The major form of irANP in the frog lymph heart was high molecular weight on reverse-phase and gel permeation high performance liquid chromatography as in the frog atria and ventricles. The frog lymph heart, as well as frog atria and ventricles, was shown to express mRNA coding for ANP. Dense core secretory granules similar to those observed in the mammalian atria were also found in the frog lymph heart. The presence of irANP and the expression of ANP gene in the frog lymph heart suggest that the lymph heart may participate in the regulation of homeostasis of lymph circulation and blood volume change through the synthesis and release of ANP.

Animals↗

PubMed1992

Ovarian atrial natriuretic peptide during the rat estrous cycle.

The changes in ovarian levels of immunoreactive atrial natriuretic peptide (irANP) and arginine vasopressin (irAVP) were observed during the estrous cycle of rat. We also demonstrated the synthesis of ovarian ANP. In adult 4-day cycling rats, ovarian level of irANP was found to be the highest on proestrus and was to be the lowest on diestrus. Ovarian irANP level inversely correlated with ovarian level of irAVP. On reverse-phase HPLC, two distinct peaks of ovarian irANP, high and low molecular weight forms, existed in the each stage of the estrous cycle. However, no significant changes in plasma and atrial concentrations of ANP were observed during the cycle. The rat ovary contained mRNA coding for ANP. These data showing the synchronized cyclic change of ovarian irANP and irAVP with the estrous cycle suggest that the ovary locally synthesizes ANP and ovarian ANP may play regulatory roles on the follicular fluid dynamics.

Analysis of Variance↗

PubMed1992

Point mutation at codon 12 of the c-Ha-ras gene in human gastric cancers.

The molecular mechanisms of the carcinogenic process of gastric cancer have not been fully understood yet. In order to know whether c-Ha-ras gene is being involved in the process of gastric carcinogenesis, 8 gastric cancer cell lines, 8 cases of gastric cancer and same number of adjacent dysplasia were analyzed for the presence of mutation at codon 12, 13 and 61 of the c-Ha-ras gene by using polymerase chain reaction (PCR) and mutant-specific oligonucleotide hybridization. Point mutations at codon 12 of the c-Ha-ras gene were found in 2 out of 8 gastric cancer and dysplasia samples in one case, but we found no mutation at codon 13 or 61 of the c-Ha-ras gene. These results suggest that the frequency of mutation of the c-Ha-ras gene detected by sensitive PCR technique is low indeed, however it would be notable that such a genetic change has been detected in the dysplastic lesion of the gastric cancer patient.

Base Sequence↗

PubMed1992

Effect of porcine bone morphogenetic protein on healing of bone defect in the rabbit radius.

Segmental long bone defects due to infection or trauma is a difficult problem to manage in patients. We studied the effect of porcine bone morphogenetic protein (pBMP) on healing of defects in the rabbit radius. Porcine BMP was separated and purified from the tibia and femur of pigs by repeated solubilization and precipitation of the protein with different concentrations of urea and GuHCl. The osteoinductive activity of pBMP was confirmed by bioassay using No. 615 mice. In rabbits, about a 15 mm length of radii were removed and 20 mg of pBMP was implanted in the defected area with fibrin sealant (FS), while only FS was implanted in controls. Union of the affected area was observed in 6 weeks in the experimental side. There was no definite evidence of bone bridging across the affected area in the controls. This suggests that pBMP has a bone forming activity in other species and the clinical use of pBMP in treating patients with segmental bone defects is promising.

Animals↗

PubMed1992

The effect of Dermatophagoides pteronyssinus allergens on proliferation and CD23 antigen expression of peripheral blood lymphocytes from atopic patients.

The low affinity IgE receptor (Fc epsilon RII/CD23) has been proposed to be involved in the regulation of IgE synthesis. The present study was undertaken to investigate the responses to in vitro stimulation by allergen (Dermatophagoides pteronyssinus; D.p) and/or interleukin-4 (IL-4) of peripheral blood lymphocytes (PBLs) isolated from atopic and non-atopic subjects. IL-4 induced up to 5 fold increase in CD23 expression on PBLs from both atopic patients and normal controls, whereas the D.p extract increased CD23 expression on cells from 7 of 8 atopic donors and from 2 of 8 normal controls. The combination of IL-4 and allergen had an additive effect of CD23 expression. PBLs from 6 of 8 atopic patients but 1 of 8 normal controls showed significant proliferative responses to D.p extract whereas IL-4 did not induce any cell proliferation. The dose of D.p extract required for the maximal CD23 expression was 20 fold higher than that for cell proliferation. These results imply that allergen stimulation, presumably through proliferating allergen specific T cells which secrete IL-4, activates B cells from most atopic donors and a few non-atopic donors resulting in increased CD23 expression. This allergen-mediated CD23 expression may play an important role in specific IgE production.

Allergens↗

PubMed1991

Identification of major allergens from the house dust mites, Dermatophagoides farinae and Dermatophagoides pteronyssinus, by electroblotting.

The allergens were separated from the extracts of house dust mites by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and identified by autoradiography. Over 30 protein bands of the whole body extract of Dermatophagoides farinae were apparent on 10-20% gradient SDS-PAGE, and 13 bands with MW between 93KD and 12KD bound with specific IgE antibodies in patients' sera sensitive to house dust mites. The major allergenic component of the whole body extract of D. farinae was the protein of MW 14-15KD, which was detected in 95.7% of 47 patients' sera sensitive to house dust mites. The extract of Dermatophagoides pteronyssinus supplied by Bencard Company, England was thought to contain feces enriched material as noted in a few broad protein bands on SDS-PAGE. Seven allergenic components were shown by autoradiography. The protein band of MW 14-15KD was one of the most frequently revealed allergens on autoradiography, which has appeared in 32.5% of 40 patients' sera sensitive to house dust mites. The electrobotting technique used in the present study was fast, convenient and highly useful for both the identification of allergen components and the screening of specific IgE antibody. The individual variations of IgE immune responses to the allergenic components of the two house dust mites were discussed.

Allergens↗

PubMed1991

Association of Helicobacter pylori with gastritis and peptic ulcer diseases.

The occurrence of Helicobacter pylori(H.pylori) and its relationship with gastric mucosa were studied by light and electron microscopy and culture of biopsy specimens from gastric mucosa of 160 patients with upper gastrointestinal symptoms. H. pylori were present in 96.6% of patients with active chronic gastritis, 100% of patients with duodenal ulcer and 76.9% of patients with gastric ulcer, while present in only 6.3% of individuals with histologically normal gastric mucosa. The bacteria colonized the antral mucosa more frequently than the body or than the duodenal cap mucosa. The bacteria were rarely seen in the intestinalized epithelium per se, but there was no significant difference in prevalence of H. pylori between gastritis with intestinal metaplasia and gastritis without intestinal metaplasia. H. pylori could be seen in close association with the surface of gastric epithelial cells below the mucus layer without evidence of intracellular parasitism, All of the strains tested were susceptible to penicillin, erythromycin, and most of them susceptible to tinidazole and bismuth salts. It is concluded that H. pylori are highly associated with gastritis and peptic ulcer diseases and its prevalence rates in patients with those diseases is higher than in developed countries. This strong association of H. pylori infection with gastritis and peptic ulcer diseases suggest a possible etiologic role for the bacterium in those diseases.

Adolescent↗

PubMed1991

Identification of mutagenic site of c-H-ras oncogene damaged by N-acetoxyacetylaminofluorene(AAAF).

A molecularly cloned human cellular H-ras (c-H-ras) oncogene(pbc N1 plasmid) was treated with N-acetoxyacetylaminofluorene (AAAF) in vitro and subcloned into E.coli. This was done to identify the mutational changes at specific codons of the gene. Guanine nucleotides were identified as the major AAAF binding site of the DNA adduct formed. Base changes in codons 12 and 61 were determined by the analysis of restriction fragment length polymorphism (RFLP) and site specific oligonucleotide hybridization. RFLP was observed due to the loss of the Hpall recognition site at codon 11 and 12 of AAAF-treated c-H-ras gene. Hybridization of AAAF treated c-H-ras with 32P-labeled oligonucleotide probes for the mutant alleles of codon 61 showed no substitutions at codon 61. From these results, it is assumed that AAAF treatment in vitro caused mutation at codon 12 but not at codon 61 of the c-H-ras oncogene and that codon 12 is the primary target of mutation by AAAF.

Acetoxyacetylaminofluorene↗

PubMed1990

Natural killer cell-mediated lysis of herpes simplex virus-infected fibroblasts: inability to detect soluble factors that contribute to lysis.

We investigated the role of soluble factors in natural killer (NK) cell-mediated lysis of herpes simplex virus (HSV)-infected cells. Supernatants generated by incubating human peripheral blood mononuclear cells with HSV-infected human fibroblasts contained tumor necrosis factor (TNF) and lysed uninfected U937 cells, but not HSV-infected fibroblasts. U937 cells, but not HSV-infected fibroblasts, were lysed when exposed to recombinant TNF (rTNF) for 18 hr. NK cell-mediated lysis of HSV-infected fibroblasts was not inhibited by addition of anti-TNF or anti-lymphotoxin (LT) antibodies to cytotoxicity assays. Thus, a role for soluble factors, and in particular TNF and LT, in NK cell-mediated lysis of HSV-infected cells could not be demonstrated.

Cytotoxicity, Immunologic↗

PubMed1990

Analysis of the state of posttranslational calmodulin methylation in developing pea plants.

A specific calmodulin-N-methyltransferase was used in a radiometric assay to analyze the degree of methylation of lysine-115 in pea (Pisum sativum) plants. Calmodulin was isolated from dissected segments of developing roots of young etiolated and green pea plants and was tested for its ability to be methylated by incubation with the calmodulin methyltransferase in the presence of [(3)H]methyl-S-adenosylmethionine. By this approach, the presence of unmethylated calmodulins were demonstrated in pea tissues, and the levels of methylation varied depending on the developmental state of the tissue tested. Calmodulin methylation levels were lower in apical root segments of both etiolated and green plants, and in the young lateral roots compared with the mature, differentiated root tissues. The incorporation of methyl groups into these calmodulin samples appears to be specific for position 115 since site-directed mutants of calmodulin with substitutions at this position competitively inhibited methyl group incorporation. The present findings, combined with previous data showing differences in the ability of methylated and unmethylated calmodulins to activate pea NAD kinase (DM Roberts et al. [1986] J Biol Chem 261: 1491-1494) raise the possibility that posttranslational methylation of calmodulin could be another mechanism for regulating calmodulin activity.

Journal Article↗

PubMed1990

Studies on rat liver nuclear DNA damaged by chemical carcinogen (3'-Me DAB) and AP DNA endonuclease. I. Purification and some properties of AP DNA endonucleases in rat liver chromatin.

Three kinds of apurinic/apyrimidinic (AP) DNA endonuclease, APcI, APcII, APcIII, were purified from rat liver chromatin through 1M KCl extraction, DEAE-trisacryl ion exchange chromatography. Sephadex G-150 gel filtration and AP DNA cellulose affinity chromatography. Activities of the purified APcI, APcII and APcIII were 62.5, 83.3 and 52.0 EU/mg of protein, respectively. Molecular weights of APcI, APcII and APcIII, each consisting of a single polypeptide, were 30,000, 42,000 and 13,000, and isoelectric points of them were 7.2, 6.3 and 6.2, respectively. Three enzymes showed different substrate specificities; APcI acted only on AP DNA, and APcII acted on both AP DNA and UV DNA, while APcIII acted on 3'-methyl-4-monomethylaminoazobenzene (3'-Me MAB) DNA adduct as well as AP DNA and UV DNA. These results indicate that three kinds of AP DNA endonuclease present in rat liver chromatin have structural and functional diversities.

Animals↗

PubMed1990

Studies on rat liver nuclear DNA damaged by chemical carcinogen (3'-Me DAB) and AP DNA endonuclease. II. Kinetic properties of AP DNA endonucleases in rat liver chromatin.

An experiment was designed to investigate the reaction mechanism of AP (apurinic or apyrimidinic) DNA endonucleases (APcI, APcII, APcIII) purified from rat liver chromatin. Sulfhydryl compounds (2-mercaptoethanol, dithiothreitol) brought about optimal activities of AP DNA endonucleases and N-ethylmaleimide or HgCl2 inhibited the enzyme activities, indicating the presence of sulfhydryl group at or near the active sites of the enzymes. Mg2+ was essential and 4mM of Mg2+ was sufficient for the optimal activities of AP DNA endonucleases. Km values of APcI, APcII and APcIII for the substrate (E. coli chromosomal AP DNA) were 0.53, 0.27 and 0.36 microM AP sites, respectively. AMP was the most potent inhibitor among adenine nucleotides tested and the inhibition was uncompetitive with respective to the substrate. The Ki values of APcI, APcII and APcIII were 0.35, 0.54 and 0.41mM, respectively. The degree of nick translation of AP DNAs nicked by APcI, APcII and APcIII with Klenow fragment in the presence and absence of T4 polynucleotide kinase or alkaline phosphatase were the same, suggesting that all 3 AP DNA endonucleases excise the phosphodiester bond of AP DNA strand to release 3-hydroxyl nucleotides and 5-phosphomonoester nucleotides.

Animals↗

PubMed1989

Inactivation of human hepatitis B virus DNA polymerase by pyridoxal 5'-phosphate.

Human hepatitis B virus (HBV) DNA polymerase activity was inhibited by pyridoxal 5'-phosphate (PLP) specifically and noncompetitively with respect to deoxythymidine triphosphate (DTTP). NaBH4 reduction of PLP-HBV core proteins resulted in the complete inactivation of HBV DNA polymerase, and PLP modification of the enzyme was though to be mediated through Schiff-base formation. HBV DNA polymerase has a Michaelis constant (Km) of 0.31 microM for dTTP and an apparent inhibition constant (Ki) of 0.2 mM for PLP. Its inactivation and modification by PLP may be useful in the study of not only the reaction mechanism of catalysis, but also the physicochemical nature of the enzyme.

Binding, Competitive↗